AN/ARN 126 VHF NAV
Glideslope antenna
Mounted below the RADAR antenna in the radome A semi-circular stub antenna that receives signals from ILS G/S stations and sends these signals to the #1 and #2 ARN-126 receivers
G/S stations
Provides G/S vertical deviation and signal validity during an ILS approach
LOC stations
Provides LOC lateral deviation, signal validity and station identification during an ILS approach
Purpose
Provides reception of VHF Omnirange (VOR), localizer (LOC), marker beacon, and glideslope (G/S) (instrument landing systems) The number 1 system is used primarily by the pilot, the number 2 system is used primarily by the copilot system. Either system can be selected through navigation instrument switching (NIS)
MB stations
Provides the pilots with audio and visual indication when flying over the Marker Beacon
Tuning operation
The VOR 1 and 2 are tuned to a valid frequency via the CDNU NAV page When VOR/ILS is selected via the NAV select switch, the VOR deviation to/from indication and system validity are provided to the ADI/HSI
Receiver purpose
The receiver contains three separate receivers • VOR and LOC receiver • Glideslope receiver • Marker beacon receiver They are all automatically tuned when a frequency is selected. Both receivers are identical but the marker beacon is only active in the number 1 receiver.
Receiver location
The receivers for the ARN-126 are both located in the LH underdeck rack
Marker beacon purpose
Illuminates marker beacon lights and initiates a tone when passing through the outer, intermediate and inner ground stations Receives the RF from the marker beacon antenna Only the number one receiver provides marker beacon information
VOR operation
Receives the VHF frequency from the VOR/LOC antenna Provides audio to the ICS if selected Provides VOR bearing to • Pilot and Co-pilot NAV select switches • Pilot and Co-pilot BDHI pointer select switches • TSO Right hand BDHI pointer select switches • NIS (Navigation instrument switching system)
Localizer operation
Receives the VHF frequency from the VOR/LOC antenna Vertical deviation is displayed on the ADI and HSI Provides audio to the ICS if selected.
Power source
Each VHF NAV system requires 28 VDC and 26 VAC 400 HZ for operation 28 volts ESS DC power Copilot upper CB panel #1 VOR/ILS #2 VOR/ILS 26 volts AC Supplied the compass transformers #1 VOR/ILS #2 VOR/ILS
Marker beacon antenna
Flush mounted in the bottom of the left wheel well fairing, forward section Functions only with the #1 receiver
Directional Antennas
VHF NAV antennas protrude horizontally from either side of the vertical stabilizer Receives RF signals from the tuned ground station
Glideslope purpose
Vertical deviation is displayed on the ADI and HSI The glideslope interface interacts with the GPWS. Audio and visual warning can be supplied when deviation from glideslope is detected when at and below 200ft AGL